The present invention relates generally to hermetic compressors and more particularly to energy efficient compressors using fluorocarbon refrigerants. An area of interest in the compressor art is how to construct a more efficient and quieter compressor.
One area that has received attention is that of noise generation and suppression within the compressor system. A majority of compressors include suction and discharge valves that open and close thereby creating noise. This noise is irritating and disruptive, particularly in residential applications of compressor systems.
It is well known that if oil within the compressor is caused to froth or foam, there is a reduction in the sound transmitted from the compressor. Accordingly, an impeller, generally in the form of paddles, has been placed on the lubricant pickup tube for oil foam generation thus reducing noise of the unit. An example of this is shown in U.S. Pat. No. 4,747,471.
For many years the refrigerant of choice in hermetic refrigeration compressors has been dichlorodifluoromethane, CCl.sub.2 F.sub.2, commonly referred to as Refrigerant R-12. Recently, the scientific community has come to recognize certain environmental hazards associated with the wide-spread use of chlorofluorocarbons (CFC's) such as R-12, and particularly in regard to its adverse effect on the ozone layer. In recent years, efforts have been made to find a substitute for R-12 that is environmentally acceptable, and that may be utilized in most refrigeration applications without requiring substantial modification of the refrigeration equipment. Tetrafluoroethane refrigerants, such as R134a (1,1,1,2 tetrafluoroethane), have been identified as acceptable substitutes for R-12 in a variety of applications, and widespread use of Refrigerant R134a is expected to increase in the future. The thermodynamic properties of R134a are close to those of R-12, and since R134a is free of chlorine, it is believed to be benign to stratospheric ozone.
With the new refrigerant, new types of lubricating oils have been subject to testing. Currently, no one lubricant satisfies the needs of adequate lubrication of the compressor parts and sound reduction within the compressor.